With secondaries up to 2.6", I pretty much have followed Bryan Greer's suggested method, with a few beads about 1/8-1/10th inch thick; RTV on either aluminum, or spun plywood plugs. Used his included spacers.
For primaries, either particle board (repair/test) or plywood/aluminum backer plates with new Dob construction, RTV @ 1/4" thick, a minimum of 6 blobs at the 70-80% radius, and maybe 3 blobs inside of that, about quarter/half-dollar size. I used 1/4" nuts for spacers, a minimum of 24 hours before removing. Up to 14" size, absolutely no issues at all. Any backers of ply or PB/MDF I made a good effort of assuring stability by checking flatness, and sealing adequately.
Unless I did the analysis Preston did, I would -NOT- go as thin as he did. I have never gone that thin personally, but had to fix some who had. Thinner is better as far as collimation is concerned, but it can be a headache with distortion of the optics. Silicone in the thicknesses I outline seem to be adequate to prevent distortion from ocurring.
Mark